The present invention relates to a printing apparatus and a printhead temperature management method, and more particularly, to printhead temperature control in a printing apparatus for performing printing on a print medium by a printhead.
As a printing apparatus which is an information output apparatus in a word processor, a personal computer, a facsimile machine and the like, for outputting information of desired characters, images and the like on a sheet type print medium such as a print sheet or a film, a serial printing-type printing apparatus, which performs printing while reciprocate-scanning a printhead in a direction orthogonal to a conveyance direction of a print medium such as a print sheet, is widely used since it has advantages in its low price, reduced size and the like.
Conventionally, such printing apparatus has been widely studied and developed. For example, an ink-jet printing apparatus using an ink-jet printhead, a thermal transfer printing apparatus using a thermal printhead and the like are widely used.
In many of such printing apparatuses, as printing progresses, i.e., as the printhead is driven, the temperature of the printhead rises. When the temperature of the printhead goes into an overheated status, inconveniences occur in a printed image and the like.
To prevent this status, in some apparatuses, if a detected temperature of the printhead is equal to or higher than a predetermined value, the printing speed is lowered, i.e., the maximum drive frequency for the printhead is lowered, or printing is temporarily suspended in a standby status for a predetermined period, thereby the printhead is prevented from going into the overheated status.
However, if the maximum drive frequency for the printhead is lowered, the speed of relative movement between the printhead and the print medium upon printing must also be lowered. Thus, the construction of the drive mechanism and the control circuit and the like becomes complicated, and the cost of the entire apparatus increases.
Further, in a case where printing is temporarily suspended in the standby status for a predetermined period, if the standby period is long, the output speed is lowered in the extreme.
The present invention has as an object to provide a printing apparatus which prevents inconveniences due to temperature rise of the printhead while suppressing reduction of output speed as much as possible by a low-cost simple construction and control.
The above-described object is attained by providing a printing apparatus in which a printhead and a print medium intermittently move relatively to each other, and during a relative movement, the printhead performs printing on the print medium, comprising: temperature detection means for detecting a temperature of the printhead; comparison means for comparing the temperature detected by the temperature detection means with a predetermined threshold value; control means for controlling start of new relative movement accompanied by printing in correspondence with the result of comparison by the comparison means; and threshold value setting means for setting the threshold value in correspondence with information regarding the number of pixels for which the printhead can perform printing during one relative movement.
Another object of the present invention is to provide a printhead temperature management method for preventing inconveniences due to temperature rise of printhead while suppressing reduction of output speed as much as possible by a low-cost simple construction and control.
The above-described object is attained by providing a printhead temperature management method for a printing apparatus in which a printhead and a print medium intermittently move relatively to each other, and during a relative movement, the printhead performs printing on the print medium, comprising: a temperature detection step of detecting a temperature of the printhead; a comparison step of comparing the temperature detected by the temperature detection means with a predetermined threshold value; a control step of controlling start of new relative movement accompanied by printing in correspondence with the result of comparison by the comparison means; and a threshold value setting step of setting the threshold value in correspondence with information regarding the number of pixels for which the printhead can perform printing during one relative movement.
According to the present invention, in the printing apparatus, in which the printhead and the print medium intermittently move relatively to each other, and the printhead performs printing on the print medium during the relative movement, the temperature of the printhead is detected, then the detected temperature is compared with a predetermined threshold value, and the start of new relative movement accompanied by printing is controlled in accordance with the result of comparison. The threshold value is set in accordance with information regarding the number of pixels for which the printhead can perform printing during one relative movement.
According to the construction, if the temperature of the printhead is equal to or higher than the threshold value set in accordance with the information regarding the number of pixels for which the printhead can perform printing during one relative movement, the new relative movement accompanied by printing is not performed.
Accordingly, as a complicated construction and control are unnecessary, inconveniences due to temperature rise of the printhead can be prevented while the reduction of output speed is suppressed as much as possible.
In this case, if the control means controls so as not to start the new relative movement accompanied by printing while the temperature is equal to or higher than the threshold value, the occurrence of inconveniences due to the temperature rise of the printhead can be effectively prevented.
Further, it is preferable that the threshold value setting means includes a table of correspondence between the information and the threshold values.
Further, the information regarding the number of pixels for which the printhead can perform printing during one relative movement may be information on the length in the direction of relative movement in an area, where the printhead performs printing during the one relative movement, or information based on whether a printing mode for divisionally printing an area where the printhead can perform printing during the one relative movement with printing during plural relative movements is set or not, or information based on a division number for the divisional printing during plural relative movements.
Further, the information may be information based on the maximum number of dots for which the printhead can perform printing during the one relative movement.
It is further preferable that the printing apparatus further comprises environmental temperature detection means for detecting an environmental temperature around the printhead, and that the threshold value setting means sets the threshold value in correspondence with the information and the environmental temperature.
In addition, in a case where the apparatus has plural printheads, it is preferable that the respective printheads have the temperature detection means, and the comparison means compares the detected maximum temperature and the threshold value.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same name or similar parts throughout the figures thereof.